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Fluid Mechanics Ch-8 Buoyancy Pressure Flow Fluids • Fluids flow and alter shape • Which states of matter are fluid? • Liquid • Gas • Plasma Gasses fill and conform to their container • Chlorine gas Cl2 Plasma’s conform to magnetic fields • At PPPL they are experimenting on the fusion of hydrogen plasma Density = m/V • “rho” = mass/volume • Density of Steam = 0.598 kg/m3 • Density of Mercury = 13.6 x 103 kg/m3 Buoyancy • FB = Fg (of displaced fluid) • = mo g Archimedes Principle • Fnet = mfg - mog Ships are rated as displacing tons of seawater Fluid Pressure • P = F/A • Force/unit area • Pounds/in2 (Psi) • Or N/m2 (Pascals) 4000 N/m2 • 107 Pascal Fluid Pressure • P = F/A • Force/unit area • PSI (lbs/insquared) Pressure increases as area applied decreases • F1/A1 = F2/A2 Hydraulics at the Dentist Syringe hydraulic lift • I raise a 10 N rock with a hydraulic piston that is 13 mm in radius using water connected to a 1.5 mm radius syringe. How much force is necessary for this lift to raise the rock? Pressure as a Function of Depth • P = Po + gh Submarine Ballast Tanks • The density of the whole device is adjusted by releasing compressed air WWIII Submarine section Buoyant force results from differing pressure at depth FB=A(Po+gh2)-A(Po+gh1) FB=g(h2-h1)A FB=gV FB=mfg That’s Archimedes Principle The Coanda Effect • Fluid adheres to surfaces • Flowing fluids are directed by curved surfaces Bernouli’s Principle on Air foils • Air flowing across and air foil flows faster across the top • Pressure is lower of the air flows faster • Fnet is upward Coanda Effect breaks down at high angles of attack • The Coanda effect guides the air flow along the surface • The air flow breaks free and turbulent flow results • Stall occurs Coanda Develops First Jet engine aircraft, 1910 It crashes, he loses funding Lost technology for 30 years